<!DOCTYPE html>
<html lang="zh-cn">
    <head>
        <meta charset="UTF-8"/>
        <meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0" />
        <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
        <title>小图标与文字垂直居中对齐</title>
        <style>
            .close-btn {
                color:#fff;
                height:45px;
                line-height: 45px;
                width:120px;
                border-radius:5px;
                text-align:center;
                background: url('http://s1.mi.com/m/images/20151028/top-x.png') red no-repeat 20px center;
                background-size: 20px 20px;
            }
        </style>
    </head>
    <body>
        <div class="close-btn">关闭</div>
    </body>
</html>